I own a 93' 400E and I just replaced the timing chain and ignition switch. I tried to start the vehicle and I finally figured out that the fuel pump was not receiving voltage. I hotwired the pumps and they work fine. I'm also trying to find the fuel relay to check it. I've double checked my ignition switch and all wires are connected. If someone can help me with some ideas I'm all ears.

Problem solved - because my battery terminal was loose proper amps was not present, causing the fuel pump not to operate. Lesson learned...........

Steve, I'm having the same problem on my 86 Euro 500 SE I put in a new dash and now have no power to fuel pump.I bridged the 30 pole and the 87 pole with the fuel pump out and still no power. The fuel pump relay on 126 is on the left side fire wall next to the OVP not sure on you car.Mine will start and run if I hot wire the pumps directly.if you pull your relay number 30 is MB code for hot side all 30's will be hot..........

William Rogers..........

Steve, have you checked the amperage @ the fuel pump relay input? Bridge jack 7 and 8 it should read 6-10 amps. you will also hear the fuel pump running. I have had to replace the fuel pump relay in my 116. Is it possible you have an open in your wiring harness? Hope this helps.

The fuel pump "relay" is under the rear seat on the W124 400E.
The fuel system computer(LH-SFI) activates the relay. That computer receives signal from ignition system the the starter is cranking & then the RPM signal.

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M.B., I'm living in the '80's, and work on less sophisticated fuel control systems not the LS-SFI. Perhaps I should note the year and model prior to posting any "helpful advice". Thanks, Spencer